If all goes according to plan, the landing of the Mars 2020 Perseverance rover (“Percy”) tomorrow (February 18, 2021) will mark the start of NASA’s ninth surface mission on the Red Planet. Percy will touch down in Jezero crater on Mars, where she will set off exploring new and uncharted terrains in search of ancient signs of life. Nearly 60 years have passed since the first spacecraft were sent to Mars, and it’s inspiring (albeit sometimes unbelievable) to reflect on the progress that has been made since then. First, we sent spacecraft to fly-by, then to orbit, then to land, and finally to rove. As we’ve become more familiar with Mars over time, and as our technological capabilities have improved, our methods of and goals for exploration have evolved in turn. And with each new mission, humans have pushed the boundaries a little more—or in the case of Percy, a lot more. Here I highlight three new (and particularly challenging) aspects of the Mars 2020 mission that distinguish it from previous missions and that have the potential to significantly impact the future of Mars exploration.
Bringing Mars Back to Earth
One of the primary objectives of the Perseverance mission is to act as the first leg in a Mars Sample Return (MSR) campaign that is being planned jointly by NASA and the European Space Agency. The rover's role in this interplanetary relay race will be to collect scientifically compelling rock samples and to place these samples in designated locations on the surface. Eventually, another rover will be sent to Jezero crater to retrieve the samples that Percy stockpiled. This fetch rover will then transfer these samples into a Mars Ascent Vehicle (MAV) that will launch into orbit and rendezvous with an Earth return orbiter; one last handoff between the spacecraft, and the samples will be on their way back to Earth. Pretty cool, huh?
But let’s be clear. MSR is complex—technologically and logistically. Sample collection alone relies on an incredibly intricate and multifaceted robotic system: first the rover arm is used to drill a rock and collect drilled material in a small sample tube; the sample is then transferred into the rover’s body to undergo a series of inspections; finally, the sample tube arrives at the sealing station, where it gets hermetically sealed for the trip back home. Every step of this process requires extreme precision, and Percy may perform this task more than thirty times during her mission. Of course, Percy isn't totally autonomous, so there will also be some very real challenges for us humans to make decisions regarding where to drive, which rocks to drill (and which not to drill), and where to stash samples so that they can be accessed by the fetch rover. These decisions will spark healthy debate amongst the team, no doubt, but I would expect no less given the gravity of the task at hand. The rover can only collect a finite number of samples, and how the team chooses to handle those samples will have an impact not only on the success of this mission but on the success of the MSR campaign as a whole. This distinguishes Perseverance from prior Mars missions and increases the stakes even more.
Even if Perseverance flawlessly executes her portion of the MSR campaign, there will be a great deal more work required to get the samples back to Earth. It will take a lot of time and money, multiple missions, and new technologies that have never been used on Mars before. But the potential payoff is big. By enabling scientists to study these samples back on Earth where they have access to a much more diverse set of scientific instruments, MSR offers an opportunity for us to make significant progress in our understanding of Mars' geology and potential habitability, and it will also help us plan for future human missions to the Red Planet. Rock samples brought back to Earth from the Apollo missions are still being studied decades later, and Mars samples would be no different. With MSR, Percy will continue to provide science long after her own surface mission is complete. In this sense, Mars 2020 is more than just a mission, it’s the start of an ambitious new endeavor in planetary exploration and one that has the potential to change the way we study Mars for years to come.
Learning to Fly on Mars
Percy isn’t traveling alone. The rover is bringing along a small helicopter, Ingenuity, which will conduct a set of test flights shortly after landing—the first powered flights ever attempted on another planet. But flying a helicopter in the thin Martian atmosphere is no trivial feat. Mars’ atmospheric density is roughly a hundred times lower than Earth’s, making it harder for the helicopter to achieve lift. Ingenuity has undergone many tests in preparation for flying on Mars, including in wind tunnels with a Mars-like atmosphere. Still, we’re never able to fully simulate Martian conditions here on Earth, especially since we can’t escape our own terrestrial gravitational field. And while the lower gravity on Mars should theoretically make it easier for a helicopter to lift off the surface, nature never quite works the way we expect it to. So, all eyes will be on Ingenuity during this exciting extraterrestrial experiment.
The first of its kind, Ingenuity is what’s known as a “technology demonstration.” The helicopter flights are technically a separate project from Perseverance; if the helicopter doesn’t function as expected, it will have no impact on the overall success of the Mars 2020 mission. But if the flights are successful, they could introduce a novel way of exploring the Red Planet. In fact, the first Martian rover, Sojourner, was a technology demonstration on the Mars Pathfinder mission, and its success led to a new generation of roving vehicles on Mars. Sojourner was followed by the Mars Exploration Rovers Spirit and Opportunity, then Curiosity, and now Perseverance. So, if Ingenuity has similar success to Sojourner, it’s not far-fetched to think that more helicopters might make their way to Mars in the future.
There are many potential benefits provided by an aerial spacecraft. Not only can a helicopter cover more ground than a rover can, but it can also provide a different perspective of the Martian surface. Ingenuity has two cameras attached to it; images taken during test flights will help engineers study flight dynamics and might even be used to help decide where Percy should drive. Helicopters are able to capture the surface from above but at a much higher resolution than can be accomplished from cameras in orbit. This vantage point is incredibly useful for scoping out potentially interesting places to explore on Mars—and on other bodies across our solar system (in fact, work is already underway on the Dragonfly mission, which will send a robotic rotorcraft to Saturn’s moon Titan later this decade!).
Looking Beyond Robotic Exploration
A human mission to Mars has long been considered one of NASA’s strategic exploration objectives. But to be honest, this goal has always felt pretty far off. Whereas prior robotic missions have provided information that will help get humans safely to Mars and back, supporting human exploration has never been an explicit goal of a Mars surface mission. Not until now, that is.
One of the four stated primary objectives of the Mars 2020 mission is to acquire data and test technologies that will help prepare for crewed missions to Mars. Several new experiments onboard the rover will directly address this objective. The Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) instrument will attempt to turn Mars’ carbon dioxide atmosphere into oxygen that can be used for astronaut consumption and rocket propellent. In situ resource utilization will likely play a key role in any human surface mission, especially due to the large amount of propellent that will be needed to launch a crewed MAV off the Martian surface to return to Earth. Bringing a large reserve of propellent all the way from Earth is costly, so there is great interest in identifying Martian resources that could be utilized to produce fuel on the surface and decrease spacecraft payloads.
The Martian atmosphere is one potential propellent source and subsurface ice is another. The Radar Imager for Mars' Subsurface Experiment (RIMFAX) instrument on Perseverance is the first ground-penetrating radar ever sent to the surface of Mars. It uses radar sounding to “see” many meters below the surface. Radar instruments in orbit around Mars have revealed evidence of vast subsurface ice deposits in some parts of the planet. If this ice could be extracted from the subsurface it could be used to produce fuel in situ. An instrument like RIMFAX could aid in the identification of these ice deposits from the surface (although to be clear, we don’t anticipate such a discovery at Jezero crater).
The rover is also bringing five samples of astronaut spacesuit material, which will be used as calibration targets for the Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC) instrument. But these samples will also provide a way to study how well these materials hold up under Mars surface conditions. In particular, pervasive Martian dust and radiation at the surface pose significant challenges to human exploration, so it will be critical to design spacesuits that can provide protection and operate effectively in this harsh environment. As someone who would personally love to step foot on the Red Planet one day, I am particularly excited by this aspect of the mission. By acquiring data on Martian surface conditions and testing new innovative technologies, the Perseverance mission will help make human exploration of Mars a reality.
In many ways, the Perseverance mission represents the next evolutionary step in Mars exploration. We have been studying the surface of Mars with landers and rovers for a half-century, and honestly, we’ve become pretty good at it! It would be easy (well, easier—planetary missions are never easy) to continue down this path instead of pursuing new, riskier kinds of exploration. But to quote President John F. Kennedy, we don’t do these things “because they are easy, but because they are hard.” We do them because they challenge our collective capabilities and because the potential risks are well worth the reward of doing something for the first time in human history. Percy will attempt many firsts, and in doing so, she will help carve a new path for future robots and humans to follow, for as much as lies behind us, even more lies ahead.